Refractory bonding system

ABSTRACT

A quick-setting refractory composition comprising basic refractory, from about 0.5 to 3 weight percent active calcium oxide, from about 2.5 to 5 weight percent glassy polyphosphate and from about 1.5 to 4 weight percent dibasic calcium phosphate or tricalcium phosphate.

Umted States Patent [191 [111 3,920,464 Damiano 5] Nov. 18, 1975 [54] REFRACTORY BONDING SYSTEM 3,839,057 10/1974 Treffner et a1 106/58 [75] Inventor: John Damiano, Linden, NJ; FOREIGN PATENTS OR APPLICATIONS [73] Assignee; quigley Co Inc. New York, NY 338,503 6/1972 U.S.S.R 106/106 22 Filed: 0a. 21, 1974 OTHER PUBLICATIONS 1 Foessel et a1. Improved Phosphate-Bonded Basic Re- [21] A 516,276 fractores Ceramic Bulletin 49 (7 pp. 652-657.

[52] U.S. Cl. 106/58; 106/59; 106/63; Primary Examiner-Helen M. McCarthy 106/64 Attorney, Agent, or Firm-Connolly and I-Iutz [51] Int. CI. C04B 35/04; C04B 35/06 [58] Field of Search 106/58, 59, 63, 64, 106 57 ABSTRACT A quick-setting refractory composition comprising [56] References Cited v basic refractory, from about 0.5 to 3 weight percent UNITED STATES PATENTS active calcium oxide, from about 2.5 to 5 weight per- 3,357,842 12/1967 Bowman 106/58 cent glassy polyphosphate and from about 1.5 to 4 Neely et a1 percent calcium phosphate o tfica]- 3,473,939 10/1969 Mayberry et a1. 106/58 cium phosphate 3,479,194 11/1969 Davies et a1. 106/58 10/1971 Davies et a1. 106/59 8 Claims, No Drawings REFRACTORY BONDING SYSTEM A BACKGROUND OFiTI-IE INVENTION This invention 7 relates to refractory compositions; More specifically, it relates to an improved phosphate bond system for quick-setting basic refractory compositions; t

Basic refractory compositions useful for casting and gunning in, forexarnple, steelmaking furnaces should possessgcertain properties. These properties include the ability to develop initial set, i.e., to harden rather rapidly to a self+sustaining condition, excellent hot strength and superior resistance to erosion and slag attack.;-

Theuse of phosphates. for improving the hot strength of basic refractories has received considerable attention. US: Pat. No.. 3,390,002 discloses burned magnesite shapes having excellent tensile strength at temperatures as high as 2900F (.1600C.), formed by combining with dead-burned magnesite finely divided silica, limeyielding materials and calcium phosphate-yielding materials. in such ratio as togive phosphateswhich are substantially all calcium silicophosphates The use of polyphosphates to develop hot strength in basic refracposition can be any basic refractory grain. This includes, but isnot limited to, magnesia alone or in combination with dead-burned dolomite. The aggregate particles include various combinations of fine and coarse fractions which are well established in the art for casting and gunning refractory compositions, typical particle size distributions being illustrated in the examples which follow. it

. The finely divided aetive calcium oxide, or lime, content of the refractory composition can vary from about 0.5 vto about 3' w'eight percent. Refractories containing active lime levels below about 0.5 percent do not develop suitable initial set, 'while those with active lime contents above about 3 percent set too rapidly for practical use in casting and gunningl Preferred active lime level is about 1.0 weight percent. By finely divided active lime" is meant calcium oxide substantially all passing a 16-mesh (U.S.') screen and capable of readily reacting at room temperature with alkali metal phosphate in the presence of water to form hydrated dibasic calcium phosphate. The active lime source can be lime alone or lime combinedfwith other alkaline ear'thox;

toriesis taught in US. Pat. No. 3,304,187 where mag-' nesiain the aggregate is reacted with sodium polyphosphate to produce the bonding; other components such as lime can be present in the aggregate to promote mineralization of the magnesia and enhance the bonding effect of the polyphosphate. US. Pat. No. 3,285,758 disclosesthe addition of'a solution of ammonium phosphatescontaining specified proportions of ortho, pyro and polyphosphates to promote initial set in basic refractory intended for gunning operations. US. Pat. No. 3,357,843 teaches the addition of polyphosphates for inhibiting the popping tendency during heating of refractory compositions in which monosodium phosphate and finely dividedreactive alkaline earth metal oxide such as lime are added to provide initial set; the setting reaction presumably involves the in situ formation of ides.. A convenient, and preferred, source of the active lime is known as .16 mesh pebble lime, alightly burned dolomite which substantially all passes a 16- mesh (U.S.) screen. A typical 16 mesh pebble lime has the following chemicalanalysis: T

hydrated alkaline earth metal acid phosphate, as ex- I plained in US. Pat. No. 3,357,842.

SUMMARY OF THE INVENTION It has now been discovered that the introduction of preformed dicalcium phosphate or tricalcium phosphate into quick-setting .refractory compositions affords unexpected advantages over the results obtained .within situ formation of dicalcium phosphate from vided dibasic calcium phosphate or tricalcium phosphate.

PETAILED DESCRIPTION OF THE INVENTION The refractory compositions of this invention, since phates commercially available are generally mixtures of thepolyphospha'te having different values of n in the type fonnula and are usually characterized by an average value of'n, often referred to as the chain length of the polyphosphate. While the average chain length of the glassy polyphosphate used in the practice of this invention can vary over awide range;the preferred range is between about 10 and 30. Sodium polyphosphates are most commonly used. Examples of glassy polyphosphates of particular value are Glass H and especially l-lexaphos, trade names for water-soluble sodium polyphosphates with average chain lengths of about 21 and 13, respectively, offered by FMC Corporation, Industrial Chemicals Division, of New York, New York. The

effective range for the polyphosphate is between about 2.5 and 5 weight percent of the refractory composition.

they possess initial set, excellent hot strength and good resistance to erosion and slag attack, a'reof particular value in casting and gunning operations associated with basic steel-making furnaces. V

The particulate refractory aggregate which com- ,sic calcium phosphate or tricalcium phosphate in amounts between about 1.5 and 4 weight percent; By

prises about percent or more of the refractorycom- Polyphosphate levels below about 2.5 percent provide poor initial set and hot strength, while levels above about 5 percent generally result in rapidly diminishing hot strength. The preferred polyphosphate level is about 3.5 weight percent. 7 I

, The superior hot strengths of the refractory composition are obtained by the addition of finely divided dibafinely divided phosphate is meant phosphate substantially all passing a l-mesh (U.S.) screen. Phosphate levels outside this weight range, while offering hot strength to basic refractories, do not produce the superior bond strengths contemplated. The preferred addition is about 2.5 weight percent dibasic calcium phosphate dihydrate.

The following examples are merely illustrative and are not to be construed as limiting the invention, the scope of which is defined by the appended claims. In these examples, unless otherwise indicated, temperatures are expressed in F, compositions are in weight percent and modulus of rupture (M/R) values are in psi (kg/cm All references to mesh size in the disclosure and examples are based on the US. Sieve Series (ASTM E-11-61); see Langes Handbook of Chemistry, 11th Edition, Section 11, page 2 (1973).

EXAMPLES l-9 Quick-setting refractories of the compositions indicated in Runs 1 through 9 of Table l were prepared as follows: The listed ingredients for each run, equivalent to kg of refractory composition, were hand blended by mixing with a trowel for about one minute. Water equivalent to 11 weight percent of the dry blend was -ing uniformly across the width of the test bar. Loading was applied through a system which increased the load from zero to the breaking value at the rate of about 300 lb/in min (0.35 kg/cm sec). Average M/R values for each of the refractory compositions are listed in Table 1.

Inspection of the tabulated results demonstrates the advantage realized by substitution of preformed dibasic calcium phosphate for its stoichiometric equivalent in the form of lime and monosodiumphosphate. The introduction of preformed dibasic calcium phosphate is exemplified by the A runs, with the respective stoichiometric counterparts represented by each corresponding B run. Aside from the case of Runs 1A and 1B, which fall below the calcium phosphate levels of the present invention, each comparison demonstrates the clear superiority resulting from the use of preformed calcium phosphate in accordance with the present invention.

Comparable advantages are obtained if dead-bumed dolomite is substituted for the 5-7 mesh, 7-16 mesh and l6 mesh'portio'ns of the magnesia or Glass 11 (avg. n 21) is substituted for Hexaphos in the refractory composition.

Table I Run 1A 18 2A 2B 3A 313 4A 48 5A 5B 6A- 68 7A 7B 8A 88 9A 9B Composition wgt 7r Refractory Magnesia" 5-7 mesh 15.0 7-16 mesh 48.0 16 mesh 4.0 V I pulverized 28.6 27.9 27.1 25.3 25.6 22.6 27.6 26.9 26.1 24.3 24.6 21.6 26.1 25.4 24.6 22.8 23.1 20.1 Hexaphos 2.5 2.5 2.5 2.5 2.5 2.5 3.5 3.5 3.5 3.5 3.5 3.5 5.0 5.0 5.0 5.0 5.0 5.0 CaO 0.9 1.2 0.9 1.7 0.9 2.2 0.9 1.2 0.9 1.7 0.9 2.2 0.9 1.2 0.9 1.7 0.9 2.2 CaHPO .2H,O 1.0 0 2.5 0 4.0 0 1.0 0 2.5 0 4.0 0 1.0 0 2.5 0 4.0 0 NaH=P0 0 1.4 O 3.5 0 5.7 0 1.4 0 3.5 0 5.7 0 1.4 0 3.5 0 5.7 Avg. M/R. psi at 2,300F 69 135 171 101 165 56 104 77 183 123 179 104 131 87 163 53 130 (k lcm at l260C) 4.9 9.5 12.0 7.1 11.6 3.9 7.3 5.4 12.9 8.6 12.6 7.3 9.2 6.1 11.5 3.7 9.1 3.2

(1) Magnesia particle size distribution (U.S. screens):

5-7 mesh through 5 mesh, retained on 7 mesh 7-16 mesh through 7 mesh, retained on 16 mesh 16 mesh all through 16 mesh, 60-80 weight percent through 325 mesh (2) Hexaphos-FMC Corp.; glassy sodium polyphosphate, avg. n 13 (3) CaO-Mallinekrodt Chem. Works; purified powder (16 mesh) (4) Call PO. 2H,0-Staufler Chem. Co.; powder. NF grade (100 mesh) (5) NaHgPp Fisher Scientific (30.; powder, tech grade then added and the mixing was continued for an additional minute to give a mixture of good casting consistency. The wet blend was cast into bars using 2 X2 X 9 inches (5.1 cm X 5.1-cm X 22.9 cm) molds. The bars were allowed to set for about 5 hours and were then removed from the molds and air dried at about 220F (105C) overnight.

The refractory compositions were tested for hot modulus of rupture (M/R) by the following technique: Three dried test bars each for paired runs (Runs 1A and 1B, Runs 2A and 28, etc; a total of 6 bars) were placed into a MIR test furnace of inside space about 3 X 2 X 2.5 feet (90 cm X 60 cm X 75 cm) containing two parallel 1.5 inches (3.8 cm) diameter aluminum rods with their axes 5.25 inches (13.3 cm) apart, the bars being centrally located perpendicularly across the rods. The fumace was heated to 2300 1 10F (1260 6C) over a period of about 2 hours and held at that temperature for 5 hours. The bars were then broken individually at 2300F(12 60C) at lO-minute intervals using an aluminum breaker bar that applied central point load- EXAMPLES 1 0-1 2 Quick-setting refractory compositions were prepared and tested as Runs 10 through 12 following the procedures of Examples 1-9. The compositions tested and the test results are shown below. Casting compositions containing greater than 3 percent CaO set too quickly to allow proper casting while those containing much less than 0.5 percent CaO did not set.

(1) Component sources same as in Table l 5 EXAMPLE 13 The procedures for the preparation and testing of Run 5A were followed with the following quicksetting composition:

Component Wgt 7c Refractory Magnesia 5-7 mesh 7-16 mesh l6 mesh pulverized Hexaphos CaHP .2H O l6 mesh pebble lime" 92.6 l5.0 48.0 l4.0 l5.6

percent active C210). Other components source same as Run A. The average hot MIR was 175 psi (l2.3 kglcm).

EXAMPLE l4 "Pfizer E-Z Flo Quicklime (partially humed dolomite containing about 60 weight I 5 cent finely divided active calcium oxide, from about 2.5 to 5 weight percent glassy alkali metal or ammonium polyphosphate and from about 1.5 to 4 weight percent preformed finely divided dibasic calcium phosphate.

2. The composition of claim 1 wherein said particulate refractory comprises magnesia.

3. The composition of claim 1 wherein said particulate refractory comprises dead-burned dolomite.

4. The composition of claim 1 wherein said glassy polyphosphate has an average chain length of from about 10 to 30.

5. The composition of claim 1 wherein said calcium oxide is in the form of l6 mesh pebble lime.

6. A refractory composition comprising about 1.0

weight percent active calcium oxide substantially all passing a l6-mesh screen, about 3.5 weight percent glassy sodium polyphosphate of average chain length of about 13 and about 2.5 weight percent dibasic calcium phosphate dihydrate substantially all passing a mesh screen, the remainder of the composition being particulate basic refractory.

7. The composition of claim 6 wherein said calcium 'oxide is in the form of pebble lime.

8. The composition of claim 6 wherein said particulate refractory comprises magnesia.

PC(Qu) 5619 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIN PATENT NO. 3,920,464

DATED NOVEMBER 18, 1975 lN\/ ENTOR(S) JOHN DAMIANO it is certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, Table 1, line 4 of footnote n (1) should read -l6 mesh all through 16 mesh, 0-20 weight percent through 325 mesh Column 3, Table I, line 5 of footnote n (l) (which line was omitted from the patent) should read --pulverized all through 16 mesh, 60-80 weight percent through 325 mesh-.

Column 3, Table I, footnote n (3) should read CaO Ma'llinckrodt Chem. Works; purified powder (-16 mesh) Efiigncd and Sealed this Twenty-seventh Day Of July 1976 [SEAL] Arrest:

C. MARSHALL DANN Commissioner ufParents and Trademarks RUTH C. MASON Arresting Officer 

1. S QUICK-SETTING REFRACTORY COMPOSITION CONSISTING ESSENTIALLY OF AT LEAST ABOUT 85 WEIGHT PERCENT PARTICULATE BASIC REFRACTORY, FROM ABOUT 0.5 TO 3 WEIGHT PERCENT FINELY DIVIDED ACTIVE CALCIUM OXIDE, FROMABOUT 2.5 TO WEIGHT PERCENT GLASSY ALKALI METAL OR AMMONIUM POLYPHOSPHATE ANDFROM ABOUT 1.5 TO 4 WEIGHT PERCENT PREFORMED FINELY DIVIDED DIBASIC CALCIUM PHOSPHATE.
 2. The composition of claim 1 wherein said particulate refractory comprises magnesia.
 3. The composition of claim 1 wherein said particulate refractory comprises dead-burned dolomite.
 4. The composition of claim 1 wherein said glassy polyphosphate has an average chain length of from about 10 to
 30. .
 5. The composition of claim 1 wherein said calcium oxide is in the form of -16 mesh pebble lime.
 6. A refractory composition comprising about 1.0 weight percent active calcium oxide substantially all passing a 16-mesh screen, about 3.5 weight percent glassy sodium polyphosphate of average chain length of about 13 and about 2.5 weight percent dibasic calcium phosphate dihydrate substantially all passing a 100-mesh screen, the remainder of the composition being particulate basic refractory.
 7. The composition of claim 6 wherein said calcium oxide is in the form of pebble lime.
 8. The composition of claim 6 wherein said particulate refractory comprises magnesia. 